PCA9534 IO expander

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The Texas Instruments PCA9534 IO expander IC allows you to configure 8 digital pins as inputs or outputs. Each pin is individually configurable, and can trigger an external interrupt pin on any state change. The chip communicates via I2C, making it quite easy to interface.

The chip also has 3 additional pins used for setting the bus address. Simply ground all three pins to utilize the base address, or tie one or more pins high via a resistor to set a different address. This means you could in theory chain up to 8 devices on a single I2C bus (64 IO pins).

Reading individual bits simply requires the application of a bit mask. To remind you, here is a conversion table for decimal, hex and binary. Here is an example, and I will put together a collection of examples and upload them to github soon.